Implantable arrhythmia therapy devices such as pacers and defibrillators typically include a power source such as a battery, an electrode, and a controller. A lead carrying the electrode typically has a proximal end that is coupled to a housing that contains the power source and controller, and a distal end that is located in, on, or around the heart. A lead can be introduced into a heart chamber, for example.
A pacing lead typically includes at least one electrode that is configured to deliver a pacing pulse, and a conductor that couples the electrode to a signal generator. Some pacing leads also include a sensing electrode and a second conductor that couples the sensing electrode to a sensing circuit.
A defibrillation lead typically includes an anode and a cathode. For example, a typical defibrillation lead includes two coils that are coupled to anode and cathode portions of a battery. A vector is defined between the anode and cathode. The effectiveness of a defibrillation therapy is affected by the configuration of the anode and cathode, and the vector defined by the anode and cathode.
In some patients, the presence of one or more implanted leads restricts on the patient's range of motion. Moreover, in a growing patient, such as a child, the patient may outgrow a lead. In some growing patients, it can be necessary to periodically explant a pacer or defibrillator and replace the device or implant longer or different leads. Improved implantable arrhythmia therapy devices are needed.